IMP RISE

i had a interesting convo with some "spl smart guys" at finals last year an the comment "no imp rise box" came up. now that ringed in my mind for quite some time but i am wondering is this true?

My wall at my peak freq has very little imp rise... only 3 tenths...

thats not bad, i would think the only 2 factors in that would be port aera an the subs with the best cooling factor. i would think if the coils are cooler the imp wouldn't rise is that right.

most likley justing truck wanted a note that was close to his tuning freq of the enclosure. dave your far away from building to imp rise. you have a good bit to gain untill this is a issue for you IMO

Our wall was only seeing about a .2 rise. Does make figuring out loads alot easier.

thanks alan that is quite true man i am far off

just saying.. lol

yea your always saying lol i am just saying go get that civic loud lol

interesting dave, so basically you want an efficent box per say? Something thats going to yield small imp rise so if you wire at like say 0.5 you want to be at 0.9 final load correct?

jmanjr82 wrote:

interesting dave, so basically you want an efficent box per say? Something thats going to yield small imp rise so if you wire at like say 0.5 you want to be at 0.9 final load correct?

or 1.5 would be nice too lol
means i am getting all the power out this groundpounder as i can.

I had a long discussion with some cats on CA.com last year... about impedance rise. I want to see what the gurus have to say on this forum.

2 Components of Impedance:
- Resistance (DC component)
Due to nominal wire resistance + added resistance due to the coil being hot
-Reactance (AC component)
Resistance caused by the buildup of magnetic or electric fields, primarily due to the coil's inductance

Since audio signals are AC, alternating current, there's obviously a changing voltage (and current) going on. The changing current creates a voltage drop, due to the inductance of the coil, thanks to

Voltage Drop = Inductance (L) * Change in current (di/dt)

The voltage drop can be equated to an added resistance using
Voltage Drop = Current (i) * Added Resistance (R)

As you guys know, the impedance spikes at resonance, and rolls off for other frequencies (except Fs). The height of the spike is dependent on how the box, but I'm not really sure WHY or HOW


My theory: If a woofer is able to act freely (little air stiffness from the box) then the impedance spike should be minimized. For free-air, the impedance has a single spike at Fs. In a box, you get 2 spikes (or more). The severity of the spikes, should depend on how much stiffness you're adding to the woofer/box system.

My question: Do small boxes give lower impedance rise or higher?